1. Department of Electrical and Computer Engineering; NUSNNI; National University of Singapore; Singapore 117576 Singapore
2. School of Electrical and Electronic Engineering; Yonsei University; Seoul 03722 Korea
3. Singapore Synchrotron Light Source; National University of Singapore; 5 Research Link; Singapore 117603 Singapore
4. Institute of Materials Research and Engineering; 3 Research Link; Singapore 117602 Singapore
5. Laboratory for Chemical Technology; Ghent University; Technologiepark 914; 9052 Ghent Belgium